Here's why:
* "I" sound: The "i" in "bison" is a short vowel sound. It sounds like the "i" in "bit" or "fish."
* Long vowel sounds: Long vowel sounds are usually spelled with a vowel followed by a silent "e" (like in "bike" or "hope").
So, the "i" in "bison" is a short vowel sound, not a long vowel sound.